Dictionary alias names

Hi,

Most dictionaries ship with `.alias' files.  E.g., the French dictionary
comes with `francais.alias', and my understanding is that it should
allow one to type "aspell -l francais" instead of "aspell -l fr_FR" and
get the same result (Emacs' Ispell interface expects it to work, for
instance).

However, I can't get it to work.  Running "strace aspell -l francais"
reveals that `aspell' doesn't even try to look for a file called
`francais.alias' or similar.

What am I missing?

Thanks in advance,
Ludovic.